A downhole power generating apparatus comprising a low pressure chamber, a floating piston, a high pressure chamber, a first flow through path, a second flow through path, and a turbine. The low pressure chamber includes an inlet and an outlet for cycling tubing fluid. The floating piston separates the low pressure chamber into an upper and lower section. The floating piston is cyclically responsive to a cycle of tubing fluid and another cycle of tubing fluid. The first flow through path couples a fluid from the lower section of the low pressure chamber to the high pressure chamber in response to a cyclical response of the floating piston. The second flow through path couples the fluid from the high pressure chamber to the lower section in response to another cyclical response of the floating piston.